Rotary drill bits are commonly used for drilling bore holes or wells in earth formations. One type of rotary drill bit is the fixed-cutter bit (often referred to as a “drag” bit), which typically includes a plurality of cutting elements secured to a face region of a bit body. Referring to FIG. 1, a conventional fixed-cutter earth-boring rotary drill bit 100 includes a bit body 110 having generally radially projecting and longitudinally extending wings or blades 120 over the bit face 130 thereof and a plurality of cutting elements 140 are generally disposed thereon.
The blades 120 are typically characterized into three categories: primary blades 120′, secondary blades 120″ and tertiary blades (not shown). The primary blades 120′ are those that, conventionally, extend radially closest to the center of the bit body 110. The plurality of cutting elements 140 disposed on the primary blades 120′, generally encompass, in combination, the entire bit face cutting profile from near the center of the bit body 110 to the shoulder/gage regions. The secondary blades 120″ (and tertiary, when present); conventionally begin radially further away from the center of the bit body 110 and extend into the shoulder area. FIG. 2 shows a schematic side cross-sectional view of a conventional cutting element placement design along a face profile of a conventional drill bit. As can be seen, cutting elements 140′ (depicted as solid ovals and truncated ovals) are conventionally placed along the primary blades 120′ (see FIG. 1) to extend from the cone region 150 to the shoulder region 170. The cutting elements 140″ on the secondary and/or tertiary blades (depicted as dashed-lined ovals and truncated ovals) conventionally extend from the nose region 160 to the shoulder region 170.